Molybdenum is a metallic element which is most frequently used as an alloying addition in alloy and stainless steels. Its alloying versatility is unmatched because its addition enhances strength, hardenability, weldability, toughness, elevated temperature strength and corrosion resistance. Although molybdenum is primarily used in steels, its complex and unique High Melting properties have proved invaluable in a constantly expanding range of other alloy systems and chemicals. One of the unique features of molybdenum, as distinct from other heavy metals, is that laboratory tests have shown its compounds to be of low toxicity.

Molybdenum is only known to occur in a natural state chemically combined with other elements. Although a number of molybdenum-bearing minerals have been identified, the only one of commercial significance is molybdenite (MoS2) - a natural molybdenum sulphide. In ore bodies, molybdenite is generally present in grades from 0.01- 0.50% and is  often associated with the sulphide minerals of other metals, notably copper.

HISTORY

Molybdenum was not discovered until the latter part of the 18th century, and does not occur in the metallic form in nature. Despite this, its predominant mineral - molybdenite - was surely utilized in ancient times but would  have been indistinguishable from other similar materials such as lead, galena and graphite. Collectively, these substances were known by the Greek word "molybdos", which means lead-like. A 14th century Japanese sword has been found to contain molybdenum. However, it was not until 1778 that the Swedish scientist, Carl Wilhelm Scheele, was able positively to identify molybdenum. He decomposed molybdenite by heating it in air to yield a white oxide powder. Shortly thereafter, in 1782, Peter Jacob Hjelm reduced the oxide with carbon to obtain a dark metallic powder which he named "molybdenum". By the end of the 1930's, molybdenum was a widely accepted technical material. The conclusion of World War II in 1945 once again brought increased research investment to develop new civilian applications, and the post-war reconstruction of the world provided additional markets for structural steels, many of which already contained some molybdenum. The years from 1945 to the present have seen a dramatically expanding range of applications for molybdenum, its alloys and its compounds. Rising demand has been comfortably balanced by new sources of assured supply and by new processing technologies with superior recovery rates.

MINING & MILLING

The relatively low grade of most Mo ores necessitates the use of high volume low cost mining extraction techniques, most commonly:Massive open cast pits; or Underground block caving, wherein large blocks of ore are undercut and allowed to collapse under their own weight. Many molybdenum mines are amongst the most productive in the world, with the largest capable of moving over 50,000 tonnes of ore per day. Mined ore is pulverized through a series of crushers and rotating ball and/or rod mills to fine particles that may be only microns (1/1000th mm) in diameter. This liberates the molybdenite from its host rock. A water slurry of the ore is then conditioned with reagents - including some fuel or diesel oil - which coats the molybdenite particles, rendering them water-repellent. Separation by flotation takes place in aerated tanks. Molybdenite particles attach to rising air bubbles and concentrate in the surface froth which is swept into overflow troughs. Subsequent regrinding and reflotation stages increase the molybdenite content of the new concentrate stream, by steadily removing unwanted material. The final concentrate contains between 70-90% molybdenite.  If required, an acidic leach may be employed to dissolve impurities such as copper and lead.

ROASTING

The roasting process converts molybdenite concentrate into technical molybdenum oxide by the following chemical reactions:  -> These take place at 600-700 C in large multihearth furnaces or "roasters". Sulphide concentrate is rabbled from the center to the periphery of one hearth where it drops to the hearth below and is rabbled back to the center. It reacts
continuously with a steady supply of forced air during the 10 hours it takes to complete the circuit across a dozen or more hearths. The resulting technical grade molybdenum oxide typically contains a minimum of 57% molybdenum, and less than 0.1% sulphur. Desulphurisation systems remove sulphur dioxide from the effluent roaster gases.  Some of the by-product molybdenite concentrates from copper mines contain small quantities (<0.10%) of rhenium, a metallic element used in catalysts for the production of unleaded gasoline and in advanced superalloys for turbine blades of the latest jet engines. Molybdenum roasters equipped to recover rhenium are one of the principal commercial sources for this rare metal.

APPLICATIONS

• FERROUS MATERIALS
• NON-FERROUS ALLOYS
• HIGH TEMPERATURE STEELS
• HIGH STRENGTH LOW ALLOY STEELS
• CAST IRONS
• CHEMICAL APPLICATIONS
• LUBRICANTS
• MO BASE ALLOYS
• MOLYBDENUM & STEEL
• CARBURISING STEELS
• TOOL & HIGH-SPEED STEELS
• SUPERALLOYS & NICKEL BASE ALLOYS
• CATALYSTS

Molybdenum Ore Molybdenum Symbol

Symbol: Mo
Atomic Number: 42
Atomic M ass: 95.94 amu
Melting Point: 2617.0 °C
Boiling Point: 4612.0 °C
Number of Protons/Electrons: 42
Number of Neutrons: 54
Classification: Transition Metal
Crystal Structure: Cubic
Density @ 293 K: 10.22 g/cm3
Color: silverish